Biosensors capable of detecting infectious agents, and/or of detecting a serological reaction in people potentially exposed to dangerous pathogens, are fundamental to rapid biodefense screening and response processes. Biosensors based on the signaling properties of membrane proteins in living cells are being increasingly developed and used to detect pathogens, but are limited by the stringent handling requirements of living cells. The ability to retain membrane proteins in their native structure within a cell-free environment could enable new types of bio-mimetic detectors to be created that exploit the cell's natural detection mechanisms but without the inherent limitations of living cell assays. The need for novel detection methods that can detect antibody responses to pathogens and, in a revised format, biodefense pathogens themselves, is exemplified by Dengue virus (DEN), a category A biodefense pathogen that results in 100 million cases of DEN related illness annually. DEN exists as four major serotypes, and their distinction is important because sequential exposure to different serotypes increases the likelihood of developing dengue hemorrhagic fever. For such pathogens, characterizing not only the magnitude, but also the breadth, persistence, and specificity of the humoral response is an important component of evaluating candidate vaccines, and understanding pathogenesis in infected individuals. Thus, in addition to biodefense detection, the availability of a rapid, in-field sensor that can detect antibodies against such pathogens could aid in the development and administration of vaccines in endemic regions. The commercial product that will result from this proposal will be a nanometer-scale, cell-free assay system for the detection of pathogen antigens and antibodies present in biological or environmental samples. [unreadable] [unreadable]